• Journal of Korean Neurosurgical Society
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• v.51 no.4
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• pp.203-207
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• 2012

Objective: The purpose of this prospective study was to evaluate the efficacy and safety of screw fixation without bone fusion for unstable thoracolumbar and lumbar burst fracture. Methods: Nine patients younger than 40 years underwent screw fixation without bone fusion, following postural reduction using a soft roll at the involved vertebra, in cases of burst fracture. Their motor power was intact in spite of severe canal compromise. The surgical procedure included postural reduction for 3 days and screw fixations at one level above, one level below and at the fractured level itself. The patients underwent removal of implants 12 months after the initial operation, due to possibility of implant failure. Imaging and clinical findings, including canal encroachment, vertebral height, clinical outcome, and complications were analyzed. Results: Prior to surgery, the mean pain score (visual analogue scale) was 8.2, which decreased to 2.2 at 12 months after screw fixation. None of the patients complained of worsening of pain during 6 months after implant removal. All patients were graded as having excellent or good outcomes at 6 months after implant removal. The proportion of canal compromise at the fractured level improved from 55% to 35% at 12 months after surgery. The mean preoperative vertebral height loss was 45.3%, which improved to 20.6% at 6 months after implant removal. There were no neurological deficits related to neural injury. The improved vertebral height and canal compromise were maintained at 6 months after implant removal. Conclusion: Short segment pedicle screw fixation, including fractured level itself, without bone fusion following postural reduction can be an effective and safe operative technique in the management of selected young patients suffering from unstable burst fracture.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.4
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• pp.278-291
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• 1998

Fracture process of continuous fiber reinforced composites is very complex because various fracture mechanisms such as matrix cracking, debonding, delamination and fiber breaking occur simultaneously during crack growth. If fibers cause crack bridging during crack growth, the stable crack growth and unstable crack growth appear repeatedly. Therefore, it is very difficult to exactly determine tile starting point of crack growth and the fracture toughness at the critical crack length in composites. In this research, fracture toughness test for CFRP was accomplished by using acoustic emission(AE) and recording of tile fracture process in real time by video-microscope. The starting point of crack growth, pop-in point and the point of unstable crack growth can be exactly determined. Each fracture mechanism can be classified by analyzing the fracture process through AE and video-microscope. The more reliable method ior the fracture toughness measurement of composite materials was proposed by using the combination of R-curve method, AE and video microscope.

• Journal of Trauma and Injury
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• v.29 no.4
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• pp.139-145
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• 2016

Purpose: The major pelvic trauma results in high mortality with associated fatal other injuries. During early stage of resuscitation, multidisciplinary approach is essential to improve the survival and outcomes. This study aims to report the effect and positive outcome of the trauma team approach on the management of hemodynamically unstable pelvic bone fracture. Methods: This retrospective review included all patients with hemodynamically unstable pelvic bone fracture admitted between March 2007 and December 2015. Patients were divided into group A, which comprised those admitted before the trauma team approach was started, and group B, which comprised those admitted after the approach was started. The advanced trauma life support protocol was followed for all patient. The comparisons between the two groups were based on medical records. Study variables included demographics, initial vital sign, injury severity score, fracture type, and injury mechanism. We analyzed the outcomes in each group with respect to the time interval for doctors' arrival, total length of stay in the emergency department (ED), time interval for computed tomography evaluation, 24-hour mortality, time interval for definitive fixation, and definitive fixation in the time-window of opportunity. Results: Fifty-three patients met the inclusion criteria. No statistically significant differences in demographic data existed between the two groups. The time interval for doctors' arrival (min, $63.09{\pm}50.48$ vs $21.48{\pm}17.75$; p=0.038) and total length of stay in the ED (min, $269.33{\pm}105.96$ vs $115.49{\pm}56.24$; p=0.023) were significantly improved. The 24-hour mortality was not significantly different between the two groups.(%, 14.3 vs 12.0; p=1.000) However, the time interval for definitive fixation and definitive fixation in the time-window of opportunity showed better results. Conclusion: The trauma team approach has positive effects, which include initial resuscitation through multidisciplinary approach and shortening the time interval to definitive fixation, on the management of hemodynamically unstable pelvic bone fracture.

• Journal of Korean Neurosurgical Society
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• v.46 no.6
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• pp.584-587
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• 2009

Although most authors regard contralateral pedicular fracture with unilateral spondylolysis as an unstable condition and recommend surgical management when immobilization fails in promoting bony healing of the fracture, few researchers have investigated the natural history of pedicle fracture or the causal relationship between symptoms and the fracture. In addition, there are no detailed guidelines that address the management of this disease. We report a rare case of contralateral pedicular fracture associated with unilateral spondylolysis at the L5 level which was successfully treated by rehabilitation with activity modification.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.213-220
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• 1998

Welding structures will be occurred sudden crack or failure by reduced fracture toughness in case of low temperature. To protect these unstable fracture is very important. Because fracture of welding part come from welding faults or residual stress, critical stress intensity factors are acquired at temperatures between $22^{\circ}C$ and $-70^{\circ}C$ from base metal, welding metal and H.A.Z. It was studied effectiveness of annealing and affection of residual stress under low temperatures. In case of fracture toughness test, it showed that fracture toughness value decreased, according to the decrease of temperature. Expecially In case that compressive residual stress was existed, $K_C$ increased.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.3
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• pp.29-36
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• 1991

This experimental research evaluated the length of crack extension with the measured compliances as the mutual comparison factors instead of the method proposed in ASTM E561-80. And this research measured the R-curves with the application to the concept of the strain energy release rate that was formulated from the inelastic energy absorbed during the crack growth. With the interpretation of R-curves, this research obtained the starting point of the unstable crack growth, and compared the values of critical fracture toughness with each other, and then examined the effects of variations of the maximum size of coarse aggregate and the thickness of specimen on the values of the critical fracture toughness.

• Journal of Trauma and Injury
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• v.32 no.1
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• pp.60-65
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• 2019

Pelvic fractures are associated with life-threatening injuries and high rates of morbidity and mortality. Management of internal blood loss associated with unstable pelvic ring injuries is paramount during the initial period. The reconstruction of the pelvic ring is of importance because it is a major contributor to the stability of the pelvic ring. We report the case of a 25-year-old man who had an unstable pelvic ring fracture combined with rupture of an obturator artery and had a successful and satisfactory treatment using minimally invasive surgery with percutaneous antegrade screw fixation.

• The Academic Congress of Korean Shoulder and Elbow Society
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• 2009.03a
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• pp.191-191
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• 2009

• Computers and Concrete
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• v.7 no.4
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• pp.387-402
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• 2010

From typical stress-axial strain curve and stress-volume strain curve of a concrete under uniaxial compression, the initiation and localization of microcracks within the interior of the specimen can be identified. The occurrence of random microcrack indicates the end of the linear elasticity, and the localization of microcrack implies formation of major crack, which triggers the onset of unstable crack propagation. The interval between initiation and localization of microcracks is characterized by a stable microcrack growth. Based on fracture behavior observed from a uniaxial compressive test of a concrete cylinder, a model has been developed to extract fundamental fracture properties of a concrete, i.e. the equivalent fracture toughness and the size of fracture process zone. The introduction of cracking Poisson's ratio accounts for tensile failure characteristics of concrete even under uniaxal compression. To justify the validity of the model proposed, tests on three-point bending have been performed to obtain the fracture toughness in accordance with two parameter fracture model and double-K fracture model. Surprisingly, it yields favorably comparable results and provides an encouraging alternative approach to determine fracture properties for concretes.

• Computers and Concrete
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• v.5 no.4
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• pp.389-400
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• 2008

In this work we simulate explicitly the dynamic fracture propagation in reinforced concrete beams. In particular, adopting cohesive theories of fracture with the direct simulation of fracture and fragmentation, we represent the concrete matrix, the steel re-bars and the interface between the two materials explicitly. Therefore the crack nucleation within the concrete matrix, through and along the re-bars, the deterioration of the concrete-steel interface are modeled explicitly. The numerical simulations are validated against experiments of three-point-bend beams loaded dynamically under various strain rates. By extracting the crack-tip positions and the crack mouth opening displacement history, a two-stage crack propagation, marked by the attainment of the peak load, is observed. The first stage corresponds to the stable crack advance, the second one, the unstable collapse of the beam.